Acylation process

ABSTRACT

The invention concerns a process for the manufacture of an acylated polymer composition comprising amylose and/or amylopectin, comprising a pre-treatment step in the presence of an acid and a hydroxycarboxylic acid, subsequent acylation and, preferably, a post-treatment step with an acid. The products obtained are useful as additives in inks, varnishes, lacquers, coatings, thickeners, adhesives or binders.

This application claims priority to European application No. EP13188991.7, the whole content of this application being incorporatedherein by reference for all purposes.

The present invention relates to an acylation process of polymercompositions comprising amylose and/or amylopectin, acylated polymercompositions comprising amylose and/or amylopectin products and the useof such acylated products in certain applications.

Acylated polymer compositions, like acetylated starch, are importantprocessed renewable raw materials which can be used in a wide range ofindustrially applied polymers. They can be applied for example in inks(e.g. WO2012059), excipients in pharmaceutics (e.g. WO11011217) andfoodstuffs (e.g. US2013236624).

CN101139401 describes degradation of starch before esterification toachieve low viscosity of the starch ester product in solution,particularly in beverages.

A common process for the acylation of polymer compositions comprisingamylose and/or amylopectin, such as starch, is the reaction of such apolymer composition with an acetylating agent, for example a carboxylicacid anhydride, which reacts with the hydroxyl functions of the polymerto form the acylated polymer composition. The physical properties of theacylated polymer composition, specifically acylated starch, aredifficult to control in the acylation process. It is therefore an objectof the present invention to provide an improved process for theacylation of polymer compositions comprising amylose and/or amylopectin,such as starch. An acylated polymer composition comprising amyloseand/or amylopectin with superior physical properties is another objectof the present invention. It is also the object of the present inventionto provide a process for the manufacture of inks, varnishes, lacquers,coatings, thickeners, adhesives or binders using the acylated polymercomposition comprising amylose and/or amylopectin with superior physicalproperties as ingredient.

It was now found that the physical properties of acylated polymercompositions, such as acylated starch, may effectively be controlled bytreating the starch before acylation with an aqueous phase comprisingone additive chosen from the group consisting of at least one acid Ahaving a pKa of equal to or less than 4.8 at 25° C. and an enzyme, and ahydroxycarboxylic acid. The physical properties can further becontrolled in an additional step after the acylation step, by treatingthe acylated polymer with at least one acid A′ with a pKa of equal to orless than 4.8 at 25° C., in the presence of water.

Consequently, in its broadest embodiment, the invention concerns aprocess for the manufacture of an acylated polymer compositioncomprising amylose and/or amylopectin having a viscosity of equal to orgreater than 50 mPas (10 w % in Triacetin at 30° C.) which comprises

-   (a) pre-treating a polymer composition comprising amylose and/or    amylopectin with an aqueous phase comprising one additive chosen    from the group consisting of at least one acid A having a pKa of    equal to or less than 4.8 at 25° C. and an enzyme, and additionally    at least one hydroxycarboxylic acid-   (b) reacting the pre-treated polymer composition with an acylating    agent to provide an acylated polymer composition comprising amylose    and/or amylopectin.

The pre-treatment step in the process allows for efficient swelling ofthe polymer composition, therefore providing pre-treated polymer whichcan be efficiently acylated. Additionally, adjustment of the viscositycan be effected in the pre-treatment step. This is further detailedbelow. Preferred polymer compositions comprising amylose and/oramylopectin are starches.

In a preferred embodiment, the invention concerns a process for themanufacture of an acylated polymer composition comprising amylose and/oramylopectin having a viscosity of from equal to or greater than 50 mPas(10 w % in Triacetin at 30° C.) which comprises

-   (a) pre-treating a polymer composition comprising amylose and/or    amylopectin with an aqueous phase comprising one additive chosen    from the group consisting of at least one acid A having a pKa of    equal to or less than 4.8 at 25° C. and an enzyme, and additionally    at least one hydroxycarboxylic acid-   (b) reacting the pre-treated polymer composition with an acylating    agent to provide an acylated starch, and-   (c) reacting the acylated polymer composition obtained in step (b)    with at least one acid A′ with a pKa of equal to or less than 4.8 at    25° C., in the presence of water.

In step (c) according to the process in of the preferred embodiment, apartial hydrolysis takes place, by which the DS controlled. Theresulting products have an improved EtOH tolerance. DS and EtOHtolerance are explained further below.

The invention further concerns an acylated polymer compositioncomprising amylose and/or amylopectin, which is obtainable by such aprocess.

Another object of the invention is an acylated polymer compositioncomprising amylose and/or amylopectin, having a degree of substitution(DS) in the range of from 2.1 to 2.9, wherein the viscosity of polymercomposition is equal to or greater than 50 mPas (10 w % in Triacetin at30° C.) and which has a EtOH tolerance of equal to or lower than 60%(v/v).

Preferred acylated polymer composition comprising amylose and/oramylopectin are starches.

A process for the manufacture of inks, varnishes, lacquers, coatings,thickeners, adhesives or binders, using acylated starch which has beenprovided by the claimed acylation process, and/or the acylated polymercomposition comprising amylose and/or amylopectin obtainable by theclaimed process and/or the acylated polymer composition comprisingamylose and/or amylopectin having a degree of substitution (DS) in therange of from 2.1 to 2.9, wherein the viscosity of polymer is equal toor greater than 50 mPas (measured in a 10 w % in Triacetin solution at30° C.) and which has an EtOH tolerance of equal to or lower than 60%(v/v), as an ingredient, is also claimed in the present invention. EtOHis intended to denote ethanol.

In the present specification, the plural form and the singular form areused interchangeably. Thus, it should be understood that the plural formalso includes the singular form and vice-versa, unless otherwiseindicated herein or clearly contradicted by context. For example, “acid”denotes a single acid or a mixture of two or more acids. As anotherexample, “starch” denotes a single starch from a single source,amylopectin/amylose composition and/or modification as well as a mixtureof two or more starches of different sources, amylopectin/amylosecompositions, modifications etc.

Polymer compositions comprising amylose and/or amylopectin generally canconsist of isolated fractions of amylose or isolated fractions ofamylopectin, or a mixture of amylose and amylopectin. Starch is apreferred polymer composition which comprises essentially a mixture ofamylose and amylopectin. Each of these materials are composed ofD-glucose units linked to one another via α-(1-4) and α-(1-6) linkages,the latter being responsible for the branches in the structure of themolecule. The ratio between the amounts of amylose and amylopectindepends on the source of the polymer, e.g. starch. According to thepresent invention, the starch employed as starting material for theacylation process can comprise predominantly amylose or, conversely,predominantly amylopectin (waxy starch). Generally, whole starch and/orisolated fractions of amylose and/or isolated fractions of amylopectincan be used. According to the present invention, the term “polymercomprising amylose and/or amylopectin” includes its preferred form,namely “starch”. The starches can be derived from any native source,wherein native relates to the fact that said starch is found in nature.Unless specifically distinguished, references to starch in thisspecification are meant to include their corresponding flours, which arestill containing proteins, such as wheat gluten (hereinafter “starch”).In the present invention, a single or several starch sources can beused. The starch may also be combined out of several sources, isolatedamylose fractions and/or amylopectin fractions, and/or derivatives likechemically or physically modified starch, which will be explainedfurther below. Typical sources for the starches are cereals, tubers,roots, legumes, fruit starches and hybrid starches. Suitable sourcesinclude but are not limited to, millet, pea, potato, sweet potato,maize, sorghum, banana, barley, wheat, rice, sago, amaranth, tapioca,arrowroot and cannay. Preferred sources according to the presentinvention are selected from the group consisting of tubers, legumes orcereals. Even more preferably, the starch source is selected from thegroup consisting of pea, potato, sweet potato, wheat and maize. Mostpreferably, maize with a high amylopectin content (waxy maize) is usedas starch source. Also suitable are starches derived from a plantobtained by breeding techniques including crossbreeding, translocation,inversion, transformation or any other method of gene or chromosomeengineering to include variations thereof.

In another embodiment of the present invention, starch is used asstarting material which is chemically and/or physically modified.

“Chemically modified starch” is intended to denote in particular thepartial chemical modification of the hydroxyl-groups in amylose and/oramylopectin. Generally, chemically modified starches which can beselected as starting material according to the present invention can beclassified as crosslinked starches, partially acetylated starches,partially etherified starches like hydroxyethylated, hydroxypropylatedand methylated starches, inorganically esterified starches, cationic,anionic (like carboxymethyl starch), oxidized starches, zwitterionicstarches, starches modified by enzymes. The preferred chemicallymodified starch is a partially hydroxypropylated starch.

In one embodiment of the present invention, the modified starch ismaltodextrin. “Physically modified starch” is intended to denote astarch that has been modified by a physical method. Generally, physicalmethods for the modification of starch include heat treatment,heat-moisture treatment, annealing, retrogradation, freezing, mechanicaltreatment, ultra high pressure treatment, gelatinization, glow dischargeplasma treatment and osmotic pressure treatment.

According to the present invention, mixtures of any of the abovementioned starches, modified starches and/or flours, derived from anysource, are also within the scope of this invention. For the sake ofsimplicity, the expression “starch” is intended to denote equally any ofthe starches, modified starches, flours and or/their mixtures, derivedfrom any source with any amylopectin/amylose ratio.

In one embodiment of the invention, the employed starch has an amylosecontent of equal to or greater than 0% and equal to or lower than 60%,based on the sum of weights of amylose and amylopectin. Preferably, theemployed starch has an amylose content of from 0% to 40% especiallypreferably, the employed starch has an amylose content of from 0% to20%.

The term “acylation of a polymer composition comprising amylose and/oramylopectin” is intended to denote the reaction of free hydroxylgroupsof the glucose units of a polymer composition comprising amylose and/oramylopectin with an acylating agent to form a corresponding acylatedpolymer composition comprising amylose and/or amylopectin. Principally,polymer composition comprising amylose and/or amylopectin correspond toformula ST(OH)₃ and reacts with a acylating agent to the correspondentacylated polymer composition comprising amylose and/or amylopectin offormula ST(OH)_(3-x)(OC(O)R)_(x), “ST” denotes the amylose and/oramylopectin polymer backbone. In the formula ST(OH)_(3-x)(OC(O)R)_(x), xdenotes the DS (degree of substitution) of the hydroxyl groups in thestarch. The DS is the average amount of acylated hydroxyl groups perglucose entity. Generally, the DS of the final acylated polymercomposition comprising amylose and/or amylopectin according to thepresent invention is from 2.1 to 2.9. Preferably, the DS of the finalacylated polymer composition comprising amylose and/or amylopectin isgreater than 2.1. More preferably, the DS of the final acylated polymercomposition comprising amylose and/or amylopectin is equal to or greaterthan 2.2. Most preferably, the DS of the final acylated polymercomposition comprising amylose and/or amylopectin is equal to or greaterthan 2.3. Preferably, the DS of the final acylated polymer compositioncomprising amylose and/or amylopectin is equal to or less than 2.9. Morepreferably, the DS of the final acylated polymer composition comprisingamylose and/or amylopectin is equal to or less than 2.85. If desired,the DS of the final acylated polymer composition comprising amyloseand/or amylopectin is equal to or less than 2.7. In a very preferredembodiment of this invention, the DS of the final acylated polymercomposition comprising amylose and/or amylopectin is from 2.3 to 2.85;in an even more preferred embodiment of this invention, the DS of thefinal acylated polymer composition comprising amylose and/or amylopectinis from 2.5 to 2.85.

In the case that partially chemically modified starch is used, x relatesto the free hydroxylgroups of the starch. In this case, a modifiedstarch ST(OR^(m))_(z)(OH)(_(3-z)), wherein R^(m i)s intended to denotethe chemically modifying group of the starting material such as methyl,reacts with an acylating agent to the correspondent acylated starch offormula ST(OR^(m))_(z)(OH)(_(3-z)-x)(OC(O)R)_(x). In this equation,R^(m) is a chemically modifying group which, in a first aspect does notbear a hydroxylgroup. Thus, in the case that chemically modified starchis used as starting material, the DS is meant to denote the sum of z andx, DS=x+z. For the sake of simplicity, DS is meant to denote x forchemically not modified starting material or chemically modifiedstarting material when, in a second aspect, R^(m) bears onehydroxylgroup, for example hydroxypropyl, and DS=x+z in chemicallymodified starting material, wherein R^(m) bears not hydroxylgroup,throughout the specification.

According to the present invention, R is a linear or branched aliphaticor cycloaliphatic group containing 1 to 18 carbon atoms, an araliphaticgroup containing 7 to 12 carbon atoms or an aromatic group containing 6to 12 carbon atoms. R can optionally be substituted by one or morehalogens, preferably fluorine, NO₂, phenyl, C(O)OR¹, OR¹ or an aromaticgroup containing to 12 carbon atoms substituted by a C₁₋₆ aliphaticgroup. R¹ is a C₁-C₄ alkyl group, which can optionally be substituted byone or more halogens, preferably fluorine.

An acylating agent is intended to denote a reactant which is capable ofreacting with the hydroxylgroups of the glucose units of a polymercomposition comprising amylose and/or amylopectin, thereby transferringan acyl group —C(O)R, —C(O)R′ and/or —C(O)R″ to form the acylatedpolymer composition comprising amylose and/or amylopectin. Acylatingagents may be, for example, carboxylic acid anhydrides (RC(O))₂O, butalso unsymmetrical carboxylic acid anhydrides corresponding to theformula (RC(O))(R″C(O))O. Other suitable acylating agents comprisecarboxylic acid halides or carbonylimidazoles.

According to one embodiment, the starch is pre-treated in step (a) withan aqueous phase containing an acid A having a pKa of equal to or lessthan 4.8 at 25° C. and a hydroxycarboxylic acid. Generally, the acid Ahaving a pKa of equal to or less than 4.8 at 25° C. is selected from thegroup consisting of mineral acids, sulfonic acids and carboxylic acids.The acid A can be either monoprotic or polyprotic. If acid A ispolyprotic, at least pKa₁ is equal to or less than 4.8 at 25° C.Preferably, acid A is selected from the group consisting of sulfuricacid, amidosulfonic acid, methane sulfonic acid, benzene sulfonic acidor phosphoric acid. Most preferably, acid A is selected from the groupconsisting of sulfuric acid and benzene sulfonic acid. Generally, morethan one acid A can be present in step (a). In this embodiment, acid Ais added in step (a) in an amount of equal to or greater than 0.001weight %, based on the amount of starch. For this purpose, the weight ofany moisture present in the starch before step (a) is not taken intoaccount when calculating the ratio of acid to starch. If more than oneacid A is added in step (a), the sum of weight percentages of the morethan one acids A is the same as the weight percentage denoted in thespecification for a single acid A. Preferably, acid A is added in step(a) in an amount of equal to or greater than 0.01 weight %. Mostpreferably, acid A is added in step (a) in an amount of equal to orgreater than 0.1 weight %. Generally, acid A is added in step (a) in anamount of equal to or less than 5 weight %. Preferably, acid A is addedin step (a) in an amount of equal to or less than 3 weight %. Mostpreferably, acid A is added in step (a) in an amount of equal to or lessthan 1.5 weight %. In a most preferred embodiment of this invention, theamount of acid A added in step (a) is from 0.3 to 1.3 weight %.

According to another embodiment, the starch is pre-treated in step (a)with an aqueous phase containing an enzyme and a hydroxycarboxylic acid.Generally, the enzyme is selected from the group of hydrolases.Preferably, the enzyme is an amylase. The amylase can be of human,animal or plant origin, bacterial source, fungicidal source orgenetically engineered microorganism source. Preferably, the amylase isselected from the group comprising glucoamylase, α-amylase, β-amylaseand γ-amylase. A very preferred enzyme is the alpha-amylase Termamyl™.The enzyme used as additive in step (a) is added in an amount equal toor greater than 5 U (enzyme unit) per g starch. Preferably, the enzymeused as additive in step (a) is added in an amount equal to or greaterthan 10 U (enzyme unit) per g starch. Even more preferably, the enzymeused as additive in step (a) is added in an amount equal to or greaterthan 15 U (enzyme unit) per g starch. Generally, the enzyme used asadditive in step (a) is added in an amount equal to or lower than 200 U(enzyme unit) per g starch. Preferably, the enzyme used as additive instep (a) is added in an amount equal to or lower than 150 U (enzymeunit) per g starch. More preferably, the enzyme used as additive in step(a) is added in an amount equal to or lower than 100 U (enzyme unit) perg starch. Most preferably, the enzyme used as additive in step (a) isadded in an amount from 20 to 90 U/g starch. Generally, enzymedegradation in step (a) is stopped by the addition of a 1 to 15% aqueousmineral acid, preferably aqueous hydrochloric acid.

According to the present invention, a hydroxycarboxylic acid is presentin step (a). The hydroxycarboxylic acid present in step (a) can be ahydroxycarboxylic acid which has from 2 to 12 carbon atoms which are atleast in one position substituted by at least one —OH-group. Preferably,the hydroxycarboxylic acid of step (a) is selected from the groupconsisting of lactic acid, glycolic acid and hydroxybutyric acid. Mostpreferably, the hydroxycarboxylic acid is lactic acid. Generally, morethan one hydroxycarboxylic acid can be added in step (a). Thehydroxycarboxylic acid can be substituted, additionally to the at leastone substitution with —OH, with one or more substituents chosen from thegroup comprising primary, secondary or tertiary amines, amides, nitro,nitrile, amido, mercapto, optionally substituted or unsubstituted alkyl,optionally substituted or unsubstituted aryl, keto-group andaldehyde-group. In the case that the optionally substituted orunsubstituted hydroxycarboxylic acid has one or more stereocenters, theterm “hydroxycarboxylic acid” as used in the present invention includesall racemates, enantiomers, diastereomers or mixtures of any of theforegoing, as well as any hydroxycarboxylic acid which bears more thanone —OH-group or other substitutent. Generally, more than onehydroxycarboxylic acid can be present in step (a).

According to the present invention, the hydroxycarboxylic acid isgenerally added in step (a) in an amount of equal to or greater than 1weight %, based on the amount of starch. For this purpose, the weight ofany water present in the starch before step (a) is not taken intoaccount when calculating the ratio of hydroxycarboxylic acid to starch.If more than one hydroxycarboxylic acid is added in step (a), the sum ofweight percentages of the more than one hydroxycarboxylic acids is thesame as the weight percentage denoted above for a singlehydroxycarboxylic acid. Preferably, the hydroxycarboxylic acid is addedin step (a) in an amount of equal to or greater than 2 weight %. Mostpreferably, the hydroxycarboxylic acid is added in step (a) in an amountof equal to or greater than 3 weight %. Generally, hydroxycarboxylicacid is added in step (a) in an amount of equal to or less than 15weight %. Preferably, the hydroxycarboxylic acid is added in step (a) inan amount of equal to or less than 12 weight %. Most preferably, thehydroxycarboxylic acid is added in step (a) in an amount of equal to orless than 9 weight %. In a most preferred embodiment of this invention,the amount of the hydroxycarboxylic acid added in step (a) is from 3.5to 8.5 weight %.

In one embodiment of the invention, step (a) and subsequent reactionsteps (b) and (c) are carried out in the presence of a carboxylic acidRC(O)OH. In this embodiment, the carboxylic acid RC(O)OH is added asreaction medium. Preferably, the acyl-group of the carboxylic acidRC(O)OH corresponds to the acyl-group transferred by the acylatingagent. More preferably, the acylating agent is a symmetrical carboxylicacid anhydride of formula (RC(O))₂O and the carboxylic acid serving asreaction medium has the formula RC(O)OH, wherein R is defined as above,and RC(O) is the same in the carboxylic acid anhydride and carboxylicacid that serves as reaction medium. Most preferably, the acylatingagent is acetic acid anhydride, and the carboxylic acid which serves asreaction medium is acetic acid. In this embodiment, generally the amountby weight of RC(O)OH added in step (a) is approximately equal to theamount by weight of starch, subtracting the potentially present moisturein the starch from the amount of starch in the calculation. Preferably,the amount of RC(O)OH is equal to or greater than 80 weight %. Morepreferably, the amount of RC(O)OH is equal to or greater than 90 weight%. Most preferably, the amount of RC(O)OH is equal to or greater than 95weight %. Preferably, the amount of RC(O)OH is equal to or less than 120weight %. More preferably, the amount of RC(O)OH is equal to or lessthan 110 weight %. Most preferably, the amount of RC(O)OH is equal to orless than 105 weight %. In a most preferred embodiment of thisinvention, the amount of RC(O)OH added in step (a) is from 95 to 105weight %. Generally, more than one carboxylic acid RC(O)OH can bepresent in step (a).

According to the present invention, the amount of water in the aqueousphase present in step (a) is generally equal to or greater than 5 weight%, based on the amount of starch. For this purpose, the weight of anywater present in the starch before step (a) is not taken into accountwhen calculating the ratio of water to starch. Preferably, the amount ofwater is equal to or greater than 6 weight %. Most preferably, theamount of water is equal to or greater than 10 weight %. Generally, theamount of water in the aqueous phase present in step (a) is equal to orless than 30 weight %. Preferably, the amount of water is equal to orless than 25 weight %. Most preferably, the amount of water is equal toor less than 20 weight %. In a most preferred embodiment of theinvention, the amount of water in the aqueous phase present in step (a)is from 10% to 20%.

According to the present invention, step (a) is generally carried out ata temperature equal to or greater than 20° C. Preferably, step (a) iscarried out at a temperature equal to or greater than 40° C. Mostpreferably, step (a) is carried out at a temperature equal to or greaterthan 60° C. Generally, step (a) is carried out at a temperature equal toor lower than 120° C. Preferably, step (a) is carried out at atemperature equal to or lower than 110° C. Most preferably, step (a) iscarried out at a temperature equal to or lower than 100° C. In a mostpreferred embodiment of this invention, step (a) is carried out at atemperature from 60 to 80° C.

In another embodiment of this invention, step (a) is carried out at atemperature from 60 to 95° C.

According to the present invention, step (a) is generally carried outduring a reaction time of equal to or more than 1 min. Preferably, step(a) is carried out during a time of equal to or more than 2 min. Mostpreferably, step (a) is carried out during a time of equal to or morethan 3 min. Generally, step (a) is carried during a time of equal to orless than 5 hours. Preferably, step (a) is carried during a time ofequal to or less than 3 hours. Most preferably, step (a) is carriedduring a time of equal to or less than 1 hour. In a most preferredembodiment of this invention, step (a) is carried carried during a timefrom 3 min to 30 minutes.

Notably the viscosity of the acylated starch is influenced by the choiceof temperature and reaction time in step (a). For high viscosity of theacylated starch, lower temperatures and/or shorter reaction times areselected. For low viscosity, higher temperatures and/or longer reactiontimes are selected.

According to the present invention, the pre-treated starch of step (a)is usually reacted with an acylating agent in step (b). As outlinedabove, an acylating agent is intended to denote a reactant which iscapable of reacting with the hydroxylgroups of the glucose units of thestarch, thereby transferring an acyl group —C(O)R, —C(O)R′ and/or—C(O)R″ to form the acylated starch. Acylation agents may be, forexample, carboxylic acid anhydrides (RC(O))₂O, but also unsymmetricalcarboxylic acid anhydrides corresponding to the formula(RC(O))(R″C(O))O. Other suitable acylating agents comprise carboxylicacid halides or carbonylimidazoles. Generally, more than one acylatingagent may be present in step (b).

This invention also relates to the formation of mixed acylated starch,where “mixed” is intended to denote more than one acylating agentpresent in the reaction, or a carboxylic acid R′C(O)OH is present in theacylation reaction with (R″C(O))₂O. In one embodiment, the acylation iscarried out with the acylating agent (R″C(O))₂O in the presence ofR′C(O)OH to give ST(OH)_(3-x-y)(OC(O)R′)_(x)(OC(O)R″)_(y). Again, DS(x+y) in the final product is usually from 2.1 to 2.9. R′ and R″ denoteindependently from another the same as R above.

In one embodiment, the acylating agent is an unsymmetrical carboxylicacid anhydride (RC(O))(R″C(O))O, wherein R is not identical with R″, andwherein mixed acylated starches are formed of the formulaST(OH)_(3-x-y)(OC(O)R′)_(x)(OC(O)R″)_(y) with a DS=(y+x), which isusually from 2.1 to 2.9 are formed in the final product, and wherein Rand R″ are defined as above.

In a preferred embodiment, symmetrical carboxylic acid anhydrides areused as acylating agent. More preferably, R in (RC(O))₂O is —C₂H₅,—CH₂CH₂F, —CH₂CHF₂ or —CH₂CF₃, meaning that the carboxylic acidanhydrides are selected from the group comprising acetic acid anhydride,difluoro acetic acid anhydride and trifluoro acetic acid anhydride. Mostpreferably, the acylating agent is acetic acid anhydride.

According to the present invention, the hydroxycarboxylic acid presentin step (a) can also act as an acylating agent for part of the—OH-groups in the starch. Therefore, R, R′ and/or R″ in the acylatedstarch may not only correspond to the RC(O), R′C(O) and/or R″C(O) groupof the one or more acylating agent and/or carboxylic acid present asreaction medium, but also to the residue defined by the residuetransferred by acylation of the hydroxylgroups with thehydroxycarboxylic acid. For example, when lactic acid is used, thestarch may partly be acylated be the group RC(O)—=CH₃CH(OH)C(O)—; whenglycolic acid is used, the starch may partly be acylated be the groupRC(O)—=CH₂(OH)C(O)—; when hydroxybutyric acid is used, the starch maypartly be acylated be the group RC(O)—=CH₃CH₂CH(OH)C(O)—.

In the specification, the term “acylating agent” is intended to includethe term “one or more acylating agents”.

According to the present invention, the acylating agent is addedgenerally in step (b) at a reaction temperature of equal to or greaterthan 40° C. More preferably, the acylating agent is added in step (b) ata reaction temperature of equal to or greater than 50° C. Mostpreferably, the acylating agent is added in step (b) at a reactiontemperature of equal to or greater than 60° C. Generally, the acylatingagent is added in step (b) at a reaction temperature of equal to orlower than 100° C. More preferably, the acylating agent is added in step(b) at a reaction temperature of equal to or lower than 90° C. Mostpreferably, the acylating agent is added in step (b) at a reactiontemperature of equal to or lower than 80° C. In a most preferredembodiment, the acylating agent is added in step (b) at a reactiontemperature from 62 to 78° C. In order to control the temperature duringthe exothermic acylation step, the acylating agent may be cooled beforeaddition to the reaction mixture, for example to a temperature of from 3to 10° C.

According to the present invention, the reaction mixture in step (b)after the addition of the acylating agent is generally heated for equalto or longer than 10 minutes. More preferably, the mixture in step (b)after the addition of the acylating agent is heated for equal to orlonger than 20 minutes. Even more preferably, the mixture in step (b)after the addition of the acylating agent is heated for equal to orlonger than 30 minutes. Generally, the reaction mixture in step (b)after the addition of the acylating agent is heated for equal to or lessthan 5 hours. More preferably, the mixture in step (b) after theaddition of the acylating agent is heated for equal to or less than 4hours. Even more preferably, the mixture in step (b) after the additionof the acylating agent is heated for equal to or less than 3 hours. Theend point for the heating of the acylation reaction mixture in step (b)generally is indicated by complete or substantially complete dissolutionof the slurry formed initially in step (a), indicating a complete orsubstantially complete acylation of the hydroxylgroups in the starch toa DS of equal to or more than 2.8, or, preferably, more than 2.9 in step(b). In a most preferred embodiment, the reaction time for the acylationreaction in step (b) is from 30 minutes to 3 hours.

According to the present invention, the reaction temperature at whichthe reaction mixture is kept in step (b) after addition of the acylatingagent, is generally equal to or higher than 40° C. More preferably, thereaction temperature at which the reaction mixture is kept in step (b)after addition of the acylating agent, is equal to or higher than 50° C.Even more preferably, the reaction temperature at which the reactionmixture is kept in step (b) after addition of the acylating agent, isequal to or higher than 55° C. Generally, the reaction temperature atwhich the reaction mixture is kept in step (b) after addition of theacylating agent, is equal to or lower than 120° C. More preferably, thereaction temperature at which the reaction mixture is kept in step (b)after addition of the acylating agent, is equal to or lower than 110° C.Even more preferably, the reaction temperature at which the reactionmixture is kept in step (b) after addition of the acylating agent, isequal to or lower than 100° C. Most preferably, the reaction temperatureat which the reaction mixture is kept in step (b) after addition of theacylating agent, is from 60° C. to 90° C.

In the specification, “amount of acylating agent “or” molar ratio ofstarch to acylating agent” also denotes the sum of amounts of acylatingagents used in step (b), when more than one acylating agent is used.

According to the present invention, complete or substantially completeacylation of starch can be achieved in step (b), with a DS of equal toor greater than 2.8, or, more preferably, 2.95. Accordingly, the molarratio of acetylating agent and starch is selected. For the calculation,the molar weight of the starch is equalized with that of its repeatingunit anhydroglucose. In the case of unmodified starch, each mole ofanhydroglucose bears basically three free hydroxylgroups which areacylated. Generally, the molar ratio of acylating agent to polymercomposition comprising amylose and/or amylopectin in step (b) is equalto or higher than 3:1. Preferably, the molar ratio of acylating agent topolymer composition comprising amylose and/or amylopectin in step (b)equal to or higher than 4:1. Even more preferably, the molar ratioacylating agent to polymer composition comprising amylose and/oramylopectin in step (b) equal to or higher than 4.5:1. According to thepresent invention, the molar ratio of acylating agent to polymercomposition comprising amylose and/or amylopectin in step (b) equal toor lower than 19:1. Preferably, the molar ratio of polymer compositioncomprising amylose and/or amylopectin to acylating agent in step (b)equal to or lower than 1:8. Even more preferably, the molar ratio ofacylating agent to polymer composition comprising amylose and/oramylopectin in step (b) equal to or lower than 7:1. Most preferably, themolar ratio of acylating agent to polymer composition comprising amyloseand/or amylopectin is from 4:1 to 5.5:1.

Additional acylating agent may be present in step (b) corresponding tothe amount of water present, and such excess of acylating agent isselected accordingly in addition to the molar ratio respective to thestarch.

According to the present invention, after completed acylation reactionin step (b), which is indicated by complete or substantially completedissolution of the reactants, the reaction mixture of step (b) issuitably cooled to a temperature of from 40° C. to 70° C. Morepreferably, the reaction mixture is cooled to a temperature of from 45°C. to 65° C. To the reaction mixture, suitably, a solution of carboxylicacid RC(O)OH, wherein the acyl residue of the carboxylic acidcorresponds to at least one acyl residue of the at least one acylatingagent of step (b), in water is added. By this, any excess of theacylating agent is converted into its corresponding carboxylic acid.

Generally, the DS of the acylated polymer composition comprising amyloseand/or amylopectin as obtained by consecutive steps (a) and (b) is equalto or greater than 2.8, and often greater than 2.95. It has been found,surprisingly, that the treatment of the acylated starch obtained byconsecutive steps (a) and (b) with an acid A′ in a step (c) in order toobtain an acylated starch with a DS of from 2.1 to 2.9 has beneficialimpact on the solubility of the acylated starch. Such an acylated starchdisplays a good solubility in a large variety of aprotic solvents suchas esters, while simultaneously having a high EtOH tolerance. This is anunexpected characteristic of the acylated starch obtainable byconsecutive steps (a), (b) and (c), which cannot be achieved by e.g.partial acylation in step (b), which would also be difficult to controlsufficiently.

Consequently, according to a preferred embodiment of the presentinvention, the acylated polymer composition comprising amylose and/oramylopectin in the reaction mixture of consecutive steps (a) and (b) isthus reacted with at least one acid A′ in step (c). In thespecification, “acid A′” is intended to denote also “at least one acidA′”, including more than one acids A′. Acid A′ is defined to be an acidhaving a pKa of equal to or less than 4.8 at 25° C. Generally, the acidA′ having a pKa of equal to or less than 4.8 at 25° C. is selected fromthe group consisting of mineral acids, sulfonic acids and carboxylicacids. Acid A′ can be either monoprotic or polyprotic. If acid A′ ispolyprotic, at least pKa₁ is equal to or less than 4.8 at 25° C.Preferably, acid A′ is selected from the group consisting of sulfuricacid, amidosulfonic acid, methane sulfonic acid, benzene sulfonic acidor phosphoric acid. Most preferably, acid A′ is selected from the groupconsisting of sulfuric acid and benzene sulfonic acid. Generally, morethan one acid A′ can be added in step (c).

According to the present invention, the acid A′ in step (c) is generallyadded to the reaction mixture at a temperature of equal to or higherthan 40° C. Preferably, the acid A′ in step (c) is added to the reactionmixture at a temperature of equal to or higher than 50° C. Even morepreferably, the acid A′ in step (c) is added to the reaction mixture ata temperature of equal to or higher than 60° C. Generally, the acid A′in step (c) is added to the reaction mixture at a temperature of equalto or lower than 100° C. Preferably, the acid A′ in step (c) is added tothe reaction mixture at a temperature of equal to or lower than 98° C.Even more preferably, the acid A′ in step (c) is added to the reactionmixture at a temperature of equal to or lower than 95° C. In a mostpreferred embodiment, the acid A′ in step (c) is added to the reactionmixture at a temperature of from 65° C. to 95° C.

According to the present invention, acid A′ is added in step (c) in anamount of equal to or greater than 0.002 weight %, based on the amountof polymer composition comprising amylose and/or amylopectin provided tostep (a). For this purpose, the weight of any moisture present in thepolymer composition comprising amylose and/or amylopectin before step(a) is not taken into account when calculating the ratio of acid topolymer composition comprising amylose and/or amylopectin. If more thanone acid A′ is added in step (c), the sum of weight percentages of themore than one acids A′ is the same as the weight percentage denoted inthe specification for a single acid A′. Preferably, acid A′ is added instep (c) in an amount of equal to or greater than 0.01 weight %. Mostpreferably, acid A′ is added in step (c) in an amount of equal to orgreater than 0.1 weight %. Generally, acid A′ is added in step (c) in anamount of equal to or less than 5 weight %. Preferably, acid A′ is addedin step (c) in an amount of equal to or less than 2 weight %. Mostpreferably, acid A′ is added in step (c) in an amount of equal to orless than 1 weight %. In a most preferred embodiment of this invention,the amount of acid A′ added in step (c) is from 0.2 to 0.8 weight %.

After addition of acid A′, the reaction mixture is generally kept at theaddition temperature as defined above, for a time defined below as “postaddition heating time”.

The post-addition heating time in step (c) is chosen according to theintended DS of the final acylated starch product. Longer post-additionheating times will result in lower DS values. Generally, thepost-addition heating time is equal to or longer than 10 minutes.Preferably, the post-addition heating time is equal to or longer than 20minutes. Even more preferably, the post-addition heating time is equalto or longer than 30 minutes. According to the present invention, thepost-addition heating time is equal to or less than 10 hours.Preferably, the post-addition heating time is equal to or less than 9hours. Even more preferably, the post-addition heating time is equal toor less than 8 hours. In a most preferred embodiment, the post-additionheating time is from 50 minutes to 6 hours.

In step (c), the reaction time, temperature and amount of A′ is chosensuch that the DS of the final product is equal to or higher than 2.05.Preferably, the DS after step (c) is equal to or higher than 2.08. Evenmore preferably, the DS after step (c) is equal to or higher than 2.1.According to the present invention, the DS after step (c) is equal to orlower than 2.95. Preferably, the DS after step (c) is equal to or lowerthan 2.92. Even more preferably, the DS after step (c) is equal to orlower than 2.9. In a most preferred embodiment, the DS after step (c) isfrom 2.1 to 2.9.

It should be noted that the total amount of water present in thereaction mixture before the addition of acid A′ in step (c) ispreferably from 5 to 20%, and should be suitably adjusted accordingly ifnot already achieved.

According to the present invention, the acylated product is preferablyrecovered after step (c) by precipitation in water. Further isolationsteps may comprise e.g. washing, filtering, spinning, pressing, dryingand/or milling.

In one embodiment of the present invention, any of the steps (a), (b)and (c) individually or in any combination may be performed in thepresence of additional solvents, reactants or reagents, such as organicsolvents like dichloromethane or toluene.

According to another embodiment, at any time during the processaccording to the present invention, solvents, reactants or reagents arerecovered from the process for further use.

The pKa value, known as acid dissociation constant, of acid A may bedetermined by standard potentiometric titration procedure.Alternatively, NMR or UV determination methods can be employed for pKadetermination.

The DS value is measured by the following method: The acylated polymeris reacted with sulfuric acid for a time of from 15 to 30 hours at atemperature of from 18 to 23° C. The reaction mixture is subjected to asteam distillation, preferably in an automated distillation apparatussuch as Vapodest 40s (Gerhardt Analytical Systems). The distillate istitrated with NaOH. The DS can be calculated from the amount of NaOHwhich is needed to neutralize the distillate.

The EtOH tolerance is a solubility parameter. It describes the amount ofethanol which is necessary to precipitate a defined amount of a product,in this case the acylated starch, from a solution of a definedconcentration in which the acylated starch is completely dissolved,preferably a solution in an aprotic solvent such as ethyl acetate. Thehigher the EtOH tolerance, the higher the tolerance of the producttowards a protic solvent in the presence of an aprotic solvent.Generally, acylated starches are either soluble in protic or aproticsolvents. It has been found, surprisingly, that the acylated starchesobtained by the process according to the present invention display agood solubility towards aprotic solvents while simultaneously toleratingprotic solvents. This makes the acylated starches according to thepresent invention very suitable for use in inks, varnishes, lacquers,coatings, thickeners, adhesives or binders, which all use a largevariety of different solvent systems.

EtOH Tolerance is measured in a turbidity titration using a T70Titration Excellence Line of Mettler Toledo with a DP5-Phototrode.

For the titration a 10% solution of starch acetate in EtOAc is prepared,and a sample of 25 mL of this 10% solution in EtOAc is automaticallytitrated with EtOH at 25° C.

For acylated polymer compositions comprising amylose and/or amylopectinwith a DS from 2.1 to 2.45, the end point of the titration is a solidcontent of precipitated acylated polymer composition comprising amyloseand/or amylopectin between 3.3% to 4.7%. The EtOH tolerance in this DSrange for the acylated polymer comprising amylose and/or amylopectinaccording to the present invention is from 53% (v/v) to 67% (v/v). Thisdenotes that 3.3% to 4.7% of the acylated polymer precipitates in asolution of from 53% (v/v) of EtOH in EtOAc to 67% (v/v) of EtOH inEtOAc. This also relates to the EtOH-dilutibility of the acylatedpolymer, which is further described below. The EtOH dilutibility in theDS range from 2.1 to 2.45 for the acylated polymer comprising amyloseand/or amylopectin according to the present invention is from 1.12 to2.03.

For acylated polymer compositions comprising amylose and/or amylopectinwith a DS from 2.46 to 2.9, the end point of the titration is a solidcontent of precipitated acylated starch between 4% to 9.5%. The EtOHtolerance in this DS range is equal to or lower than 60% (v/v).Preferably, the EtOH tolerance in this DS range is from 5% (v/v) to 57%(v/v). This also relates to the EtOH-dilutibility of the acylatedpolymer, which is further described below. The EtOH dilutibility in theDS range from 2.46 to 2.9 for the acylated polymer comprising amyloseand/or amylopectin according to the present invention is equal to orlower than 1.5. Preferably, the EtOH dilutibility in this DS range isfrom 0.05 to 1.33.

The EtOH tolerance is an alternative way to describe the“non-solvent-dilutibility”, here EtOH dilutibility, of the acylatedcompositions comprising amylose and/or amylopectin in a solvent in whichthe polymer can be well solved, which is in this case EtOAc. A solutionconsisting of acylated polymer and EtOAc is titrated against a polarsolvent, often water, but in the present invention EtOH, which will notsolve the polymer and is the non-solvent. The polymer compositioncomprising amylose and/or amylopectin in EtOAc is titrated against EtOHuntil turbidity is observed as described above, indicating flocculationof polymer precipitating out of the titrated polymer composition inEtOAc. The non-solvent-dilutibility is a term known is the literature,e.g. in J. Prieto and J. Kiene, “Holzbeschichtung”, p. 61, 2007,published by Vincentz Network GmbH (ISBN 3-87870-749-5) where it isidentified by the german term “Verschneidbarkeit”, which is defined asthe amount of non-solvent, in the present invention EtOH, which can beadded to a solution of polymer in an amount of solvent, which is EtOAcin the present invention, until gelatinization or flocculation isobserved. For example, a dilutibility of 1.12 indicates that up to 1.12parts of EtOH can be added to the solution containing acylated polymercomprising amylose and/or amylopectin and 1 part EtOAc untilprecipitation is observed. The dilutibility as used in the presentinvention not only indicates the suitability of the solvent for a givenpolymer, but, for a given non-solvent/solvent system at a givenconcentration and temperature, also the tolerance of a polymer againstthe non-solvent in its solvent. This characteristic not only related tothe DS of a polymer composition comprising amylose and/or amylopectin,but presumably is also directly dependent on the substitution pattern ofthe hydroxyl-group of the polymer composition, which is effectivelycontrolled in the process according to the present invention.

The viscosity of a fluid is a measure of its resistance to gradualdeformation by shear stress or tensile stress. For liquids, itcorresponds to the informal notion of “thickness”. Solutions of acylatedstarch can also be characterized by their viscosity, which is mainlydependent on the physical and chemical properties of the acylatedstarch, when viscosities of the same concentration, in the same solventand at the same temperature are compared. It has been found,surprisingly, that the viscosity of the acylated starch according to thepresent invention can be influenced in a desirable range by settingreaction parameters accordingly, notably the parameters of step (a).This makes the acylated starches according to the present invention verysuitable for use in inks, varnishes, lacquers, coatings, thickeners,adhesives or binders, which all use a large variety of different solventsystems and have various specific viscosity requirements in thosesolvent systems.

The acylated polymer compositions comprising amylose and/or amylopectinobtainable by the process according to the present invention possess aviscosity, measured in a 10% (w/w) solution in Triacetin at 30° C. witha rotational viscosimeter, such as Rheomat R180 (ProRheo), of equal toor greater than 50 mPas. Preferably, the viscosity is equal to or largerthan 100 mPas. Even more preferably, viscosity is equal to or largerthan 200 mPas. Generally, the viscosity is equal to or lower than 1800mPas; preferably, the viscosity is equal to or lower than 1700 mPas.Most preferred is a viscosity of equal to or lower than 1600 mPas.

Should the disclosure of any patents, patent applications, andpublications which are incorporated herein by reference conflict withthe description of the present application to the extent that it mayrender a term unclear, the present description shall take precedence.

EXAMPLES Example 1

15.5 kg of potato starch with a moisture content of 3 weight % waspre-treated with 150 g of amido sulfuric acid, 1.5 kg of lactic acid(90% w/w), 750 g of water and 15 l of glacial acetic within 1 h to 75°C. and cooled down to 67° C. within 20 min.

48 l of acetic anhydride (91.2% w/w; T=8° C.) was added in 3 portions(approx. 20 l/20 l/8 l) during 6 min.

The reaction temperature was increased from 60 to 100° C. within 25 min.

After 30 min the starch acetate was dissolved completely.

The reaction mixture was cooled down to 60° C. The acetylation reactionwas stopped by adding 15 l of 56.5 weight % acetic acid. The product wasthen was precipitated in 100 l of water.

The precipitated powder was washed until no acetic acid was detectable.

The starch acetate powder was pressed of to a solid content of approx.20 weight % and dried to a moisture content of approx. 0.5-3 weight %.

The characteristics of the starch acetate obtained were as following:

-   DS=2.81-   Viscosity (10 weight % in triacetine, 30° C.) 1510 mPas-   Soluble in ethylacetate, triacetine, chloroform

Example 2

In example 1, after the acetylation reaction is stopped, a water contentof 10-12 weight % is adjusted in the reaction mixture, the reactionmixture is heated up until a temperature between approx. 70-95° C. and0.003 weight % of concentrated sulphuric acid (95-98% w/w) is added. In1-10 h a series of different DS (DS 2.9-1.6) can be obtained

Example 3

25 kg of waxy maize with a moisture content of. 10.55 weight % wasreacted with 20.2 l of glacial acetic acid, 250 g of amido sulfuric acidand 1.4 kg of lactic acid (90% w/w) during 1.5 h at a temperature of 75°C.

72 l of acetic anhydride (91.2% w/w, T=8° C.) were added in portions(approx. 2-5 l) during 1.2 h. The reaction temperature was kept between75 and 90° C. After 3 h the starch acetate was completely dissolved. Thereaction mixture was cooled down to 50° C. 5 l of 20% w/w acetic acid inwater were added. Afterwards a water content of 10-12 weight % wasadjusted in the reaction mixture, the reaction mixture was heated upuntil a temp. between approx. 70-95° C. and 0.3 weight % of concentratedsulphuric acid (95-98% w/w) was added. In 1-10 h a series of differentDS (substitution degree 2.9-1.6) was obtained. Then 5-25 l portions ofthe reaction mixture were poured in approx. 100 l of cooled water toprecipitate the product.

The precipitated powder was washed until no acetic acid was detectable.

The starch acetate powder was pressed of to a solid content of approx.20 weight % and dried to a moisture content of approx. 0.5-3 weight %.

The characteristics of the starch acetate obtained after 4 hourshydrolysis in step c) were as following: DS=2.4

-   Viscosity (10 weight % in triacetine, 30° C.) 53 mPas-   Soluble in ethylacetate, triacetine, chloroform

The invention claimed is:
 1. A process for the manufacture of anacylated polymer composition comprising acylated amylose and/or acylatedamylopectin, having a viscosity of equal to or greater than 50 mPas (10w % in Triacetin at 30° C.), the process comprises: (a) pre-treating bycontacting a polymer composition comprising amylose and/or amylopectinwith an aqueous phase consisting of 5 to 20 weight % water, one additiveselected from the group consisting of at least one acid A having a pKaof equal to or less than 4.8 at 25° C. and an enzyme, and additionallyat least one hydroxycarboxylic acid, and optionally at least one organicsolvent selected from the group consisting of dichloromethane andtoluene, to swell the amylose and/or amylopectin; and (b) reacting thepre-treated polymer composition with an acylating agent until completedissolution of the slurry formed initially in step (a) to produce theacylated polymer composition comprising the acylated amylose and/oracylated amylopectin.
 2. A process for the manufacture of an acylatedpolymer composition comprising acylated amylose and/or acylatedamylopectin, having a viscosity of equal to or greater than 50 mPas (10w % in Triacetin at 30° C.), the process comprises: (a) pre-treating bycontacting a polymer composition comprising amylose and/or amylopectinwith an aqueous phase consisting of 5 to 20 weight % water, one additiveselected from the group consisting of at least one acid A having a pKaof equal to or less than 4.8 at 25° C. and an enzyme, and additionallyat least one hydroxycarboxylic acid, and optionally at least one organicsolvent selected from the group consisting of dichloromethane andtoluene, to swell the amylose and/or amylopectin; (b) reacting thepre-treated polymer composition with an acylating agent until completedissolution of the slurry formed initially in step (a) to produce theacylated polymer composition; and (c) reacting the acylated polymercomposition obtained in step (b) with at least one acid A′ with a pKa ofequal to or less than 4.8 at 25° C., in the presence of water.
 3. Theprocess of claim 1, wherein in step (a) the polymer compositioncomprising acylated amylose and/or acylated amylopectin is pre-treatedat a temperature in a range of from 20° C. to 85° C. for a pre-treatmenttime in a range of from 3 minutes to 30 minutes.
 4. The processaccording claim 2, wherein the at least one acid A used in step (a) andthe at least one acid A′ used in step (c) can be the same or differentand are selected from the group consisting of mineral acids, sulfonicacids and carboxylic acids, wherein the selected acids are eithermonoprotic or polyprotic.
 5. The process according to claim 1, whereinthe at least one hydroxycarboxylic acid has from 2 to 12 carbon atoms,wherein at least one said carbon atom is substituted by at least one —OHgroup.
 6. The process according to claim 2, wherein the additive is anenzyme, and wherein acid A′ in step (c) is selected from the groupconsisting of mineral acids, sulfonic acids, and carboxylic acids,wherein the selected acids are either monoprotic or polyprotic.
 7. Theprocess according to claim 1, wherein the acylating agent is selectedfrom the group consisting of carboxylic acids, symmetrical orunsymmetrical carboxylic acid anhydrides, carboxylic acid halides, andcarboxylic acid carbonylimidazoles.
 8. The process according to claim 1,wherein step (a) is carried out in the presence of a carboxylic acid,wherein the carboxylic acid corresponds to the carboxylic acid obtainedby hydrolysis of the acylating agent.
 9. The process according to claim1, wherein the polymer composition comprising amylose and/or amylopectinprovided in step (a) is selected from the group consisting of chemicallymodified starches, unmodified starches, and a mixture of chemicallymodified starches and unmodified starches.
 10. The process according toclaim 9, wherein the unmodified starch is selected from the groupconsisting of maize starch, wheat starch, potato starch, rice starch,pea starch, rye starch, millet starch, and manioc starch, and whereinthe chemically modified starch is selected from the group consisting ofchemically modified maize starch, chemically modified wheat starch,chemically modified potato starch, chemically modified rice starch,chemically modified pea, chemically modified rye starch, chemicallymodified millet starch, and chemically modified manioc starch.
 11. Theprocess according to claim 9, wherein the chemically modified starch isselected from the group consisting of crosslinked starches, acylatedstarches, hydroxyethylated starches, hydroxypropylated starches,methylated starches, oxidized starches, and cationic or anionicstarches.
 12. The process according to claim 1, wherein the time andtemperature of the pre-treatment are selected such that the viscosity ofthe final acylated polymer composition comprising acylated amyloseand/or acylated amylopectin is equal to or greater than 50 m Pas (10 w %in Triacetin at 30° C.).
 13. The process according to claim 2, whereinthe reaction time and reaction temperature of step (c) is selected suchthat the degree of substitution (DS) of the acylated starch is from 2.1to 2.9.
 14. The process according to claim 2, wherein the acylatedpolymer composition is an acylated starch.
 15. The process according toclaim 4, wherein the at least one acid A and the at least one acid A′are the same or different, and are sulfuric acid, amidosulfonic acid,benzene sulfonic acid, or phosphoric acid.
 16. The process according toclaim 5, wherein the hydroxycarboxylic acid is selected from the groupconsisting of lactic acid, glycolic acid, and hydroxybutyric acid. 17.The process according to claim 6, wherein the enzyme is an amylase. 18.The process according to claim 7, wherein the carboxylic acid anhydrideis acetic acid anhydride.